Ouch! Kourtney Kardashian is really smarting over Justin Bieber’s rude comments about their hookups and she wants a big time apology! HollywoodLife.com has the EXCLUSIVE details on how upset she is and what she wants him to do to make things right!

It’s never too late to say “Sorry!” Justin Bieber, 21, broke his code with Kourtney Kardashian, 36, to not publicly discuss their hookup sessions and now he’s got some serious explaining to do! He told radio programThe Bert Show that “I’m being used, man. What can I say?!” when asked about their fling, and while he was joking, Kourt didn’t find anything funny about it. HollywoodLife.com has EXCLUSIVELY learned she wants an apology ASAP for the apparent diss!

“Kourtney wants a major explanation and apology. She’s not the one who leaked their romance to the public. She feels like she’s being punished and it just goes to prove her initial instinct — that Justin is too young and too immature,” a source tells HollywoodLife.com EXCLUSIVELY. Kourt, you should have trusted that gut feeling because take one look at the way Justin acts and you know he wasn’t going to keep this topic under lock and key forever! Rich, spoiled and famous 21-year-olds tend to do whatever they please.

She’s especially upset over the fact that they’d agreed to not speak about their torrid affair. “They both promised each other that they would not discuss their relationship with anyone, and then he goes and disses her in public,” our source continues. Yikes, we feel for ya Kourt!

The show’s host Bert Weiss pressed Justin on the topic of Kourtney on his program that aired Jan. 5. On it, Justin said, “I’m being used, man. What can I say?!” before backpedaling a bit to reveal, “No, no, but for real, she’s great. I’ve known [the family] for years.” Ewww…that last part kind of creeps us out, that means he knew them since he was just a teen and and was probably like a little brother to them, yet now he’s hooking up with the eldest Kardashian? There’s a little bit of “ick” factor hanging over that last statement.

HollywoodLifers, do you think Justin owes Kourtney an apology for dissing their hookups?